How was antimatter discovered?
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In this section you will find answers to the following questions:
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When was antimatter discovered?
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Who did it?
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Who saw it for the first time?
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Where was it found?
On many occasions, big discoveries in science are a result of chance. However, the existence of antimatter was predicted before anybody had actually been able to observe it in the real world. How was this possible?
At the beginning of the 20th century, Physics was experiencing a revolution with the incorporation of two new theories that completely redefined our knowledge of the world: Einstein's Theory of Relativity and Schrödinger and Heisenberg's Quantum Theory. Nevertheless, the application of these ideas to the description of the atoms presented many difficulties in the early days of the theories. In 1929, the British physicist Paul Adrien Maurice Dirac wrote a formula that solved the conflict and finally explained the laws that govern the behavior of the electrons in the atom. The formula earned him the Nobel Prize in 1933.
But the formula revealed much more than that. The equation had “two solutions”. One of them was the predicted solution that described the behavior of electrons (which have negative charge). The other solution, however, suggested the existence of “positively charged electrons”. Dirac vehemently defended the existence of this particle and he called it “positron” (a combination of the terms positive and electron). During his Nobel Prize speech, Dirac defined it as "a mirror-image of the electron, having exactly the same mass and opposite charge”. Moreover, Dirac ventured the possibility that there existed stars made of antimatter in the universe.
Paul Dirac
Related scientific discoveries came by soon after this fascinating prediction. Four years after Dirac's formula, in 1932, the American physicist Carl Anderson, from the California Institute of Technology, observed a positron for the first time and succeeded in photographing it. This discovery was to a certain extent a result of chance. Anderson was investigating the behavior of cosmic rays, particles and radiation that reach us from space. He was observing their motion through a device called “cloud chamber” that makes it possible to observe the trajectory of the particles constituting cosmic rays. He had successfully identified neutrons and electrons when he also discovered certain particles that behaved in the same way as electrons, but moved in the opposite direction. It was the first irrefutable evidence of the existence of positive electrons or positrons. The discovery also earned him the Nobel Prize in 1936.
Carl Anderson and the cloud chamber
From then on the search for the remaining antimatter particles started. The negative proton, or antiproton, was found first. But this time it was not a question of chance, scientists had to design complex experiments to produce it.